1. Field of the Invention
The invention relates to a process and an apparatus for treatment of volatile organic compounds, particularly to a design to increase the humidity of untreated exhaust gas by spraying water mist thereon and then to dehumidify the humidified exhaust gas by condensation for remaining nearly the same humidity ratio of the exhaust through the pre- and post-treatment.
2. Description of the Related Art
Organic solvents are widely used in life and industry, which are easily volatilized into gas at room temperature; therefore, organic solvents are also known as volatile organic compounds. Since the majority of the volatile organic compounds are toxic and harmful to human body, a proper treatment is required for the organic compounds. During the process of the treatment, the exhaust gas is produced and contains water-soluble volatile organic compounds with high boiling point and low vapor pressure, and the water-soluble volatile organic compounds are usually separated from the exhaust gas by a condensing device. A purification device then collects the non-separated volatile organic compounds for incineration or purification treatment of condensation after adsorption and desorption.
FIG. 1 illustrates a conventional condensing device for separating water-soluble volatile organic compounds from exhaust gas, comprising a condenser 11 arranged in an exhaust gas passage 10, allowing an exhaust gas temperature therein dropped below a dew point temperature. The water-soluble volatile organic compounds are separated from the exhaust gas by adsorption of condensed water and condensation of the volatile organic compound itself. The conventional condensing device further comprises a demister 12 or a second condenser (not shown) arranged at a downstream end of the condenser 11 to allow the volatile organic compounds with smaller particle size and water vapor growing for secondary separation or condensation. Moreover, the condensate of the condenser 11 and the demister 12 or second condenser drop in a collecting tank 13 arranged under the condenser 11 and the demister 12. However, the dropped condensate in the collecting tank 13 contains the volatile organic compounds with low concentration which is hard to be recycled and reused. A great amount of waste water with a large amount of volatile organic compounds is also produced, resulting in environmental pollution.